My experience is the shielding can help a little with receiver performance, it also helps protect your radio from other interference.
With that said for normal use, I don't think it is too critical. Funny thing is that the little stamped piece of metal is probably just as or more expensive than half of the ic's on that board. So it gets pulled for cost.
The other thing to note is that some countries, especially Japan require tamper proof shields over radios so you can't swap the oscillator or muck with the circuit. The pads might just be there for a version of the radio that ships to Japan...